Plasma processing method

ABSTRACT

A plasma processing apparatus that enables polymer to be removed from an electrically insulated electrode. A susceptor of the plasma processing apparatus is disposed in a substrate processing chamber having a processing space therein. A radio frequency power source is connected to the susceptor. An upper electrode plate is electrically insulated from a wall of the substrate processing chamber and from the susceptor. A DC power source is connected to the upper electrode plate. A controller of the plasma processing apparatus determines a value of a negative DC voltage to be applied to the upper electrode plate in accordance with processing conditions for RIE processing to be carried out.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plasma processing apparatus, a plasmaprocessing method, and a storage medium, and in particular relates to aplasma processing apparatus having an electrode that is electricallyinsulated from other component elements.

2. Description of the Related Art

Parallel plate type plasma processing apparatuses are known that have asubstrate processing chamber that has therein a processing space intowhich is transferred a wafer as a substrate, a lower electrode that isdisposed in the substrate processing chamber and is connected to a radiofrequency power source, and an upper electrode that is disposed such asto face the lower electrode. In such a plasma processing apparatus, aprocessing gas is introduced into the processing space, and radiofrequency electrical power is applied into the processing space betweenthe upper electrode and the lower electrode. When a wafer has beentransferred into the processing space and mounted on the lowerelectrode, the introduced processing gas is turned into plasma throughthe radio frequency electrical power so as to produce ions and so on,and the wafer is subjected to plasma processing, for example etchingprocessing, by the ions and so on.

In the case of forming the plasma by introducing a CF type processinggas into the processing space as the processing gas, a CF type reactionproduct is produced in the processing space, and becomes attached aspolymer to a surface of each of the upper electrode and the lowerelectrode, and an inner wall surface of the substrate processingchamber. Here, because radio frequency electrical power is supplied toeach of the upper electrode and the lower electrode, a potential on thesurface of each of the upper electrode and the lower electrodefluctuates, and hence a potential difference arises between the plasmain the processing space and the surface of each of the upper electrodeand the lower electrode. Ions collide with the surface of each of theupper electrode and the lower electrode in accordance with the potentialdifference, whereby the polymer attached to the surface is removed.Moreover, the wall of the substrate processing chamber is generallygrounded, and hence a potential difference arises between the plasma inthe processing space and the inner wall surface of the substrateprocessing chamber. Polymer attached to the inner wall surface is thusalso removed through collisions with ions.

There is also known a plasma processing apparatus in which adust-collecting electrode is disposed in the processing space so as toreliably prevent polymer from becoming attached to the surface of eachof the upper electrode and the lower electrode, and the inner wallsurface of the substrate processing chamber. In such a plasma processingapparatus, a DC voltage is applied to the dust-collecting electrode,whereby the dust-collecting electrode electrostatically attracts andthus captures reaction product in the processing space (see, forexample, Japanese Laid-open Patent Publication (Kokai) No. H07-106307).

Moreover, in recent years, as semiconductor devices have becomeincreasingly highly integrated, patterns formed on wafers have been madefiner. Such making semiconductor devices finer is achieved by reducingthe light source wavelength of an exposing apparatus used inphotolithography, and at present it has come to be that an argonfluoride (ArF) excimer laser of wavelength 0.193 μm is used as the lightsource.

For a photoresist film (ArF resist film) used in photolithography usingsuch an ArF excimer laser, the etching selectivity thereof relative to asemiconductor device constituent material is insufficient, and hence itis difficult to etch the constituent material accurately using a singlelayer of such an ArF resist film as a mask.

Moreover, as patterns are made finer, it becomes impossible to make thephotoresist film thick. It is thus difficult to achieve the high etchingselectivity required of the photoresist film relative to thesemiconductor device constituent material.

As an example of a process for solving such problems, multi-layer resistprocesses have thus been developed. A multi-layer resist process is aprocess in which, to improve the functioning as a mask material inetching of the constituent material, the resist is made to bemulti-layer, whereby the target layer can be precisely processed.

Such a multi-layer resist process is described, for example, in JapaneseLaid-open Patent Publication (Kokai) No. 2002-093778. Following is abrief description of the multi-layer resist process described inJapanese Laid-open Patent Publication (Kokai) No. 2002-093778.

First, on a semiconductor device constituent material (a silicon oxidefilm type insulating film, e.g. SiO₂), there are formed in order a lowerlayer resist film (a coating type carbon film, e.g. amorphous carbon)that can be selectively etched relative to the constituent material, anoxide film (SOG film, e.g. SiO₂ or SiOC) that can be selectively etchedrelative to the lower layer resist film, and a photoresist film.

Next, the photoresist film is patterned by photolithography, and theoxide film (inorganic film) is etched using the photoresist film as amask, thus transferring the pattern of the photoresist film onto theoxide film. Next, the lower layer resist film (organic film) is etchedusing the patterned oxide film as a mask, thus transferring the patternof the oxide film onto the lower layer resist film. Processing of theconstituent material (inorganic film) is then carried out using thelower layer resist film as a mask.

Here, in an etching apparatus for the insulating film, from theviewpoint of improving efficiency, it is required that both theinorganic film etching of the silicon oxide film type insulating filmwhich is made of a silicon-based material such as SiO₂, and the organicfilm etching of the coating type carbon film which is made of acarbon-based material such as amorphous carbon be carried out in thesame chamber. In the etching of the SiO₂ material, a CF type gas such asC₄F₈ is mainly used, and to achieve a high etching rate, an etchingapparatus that enables high-electron-density high-bias etching to beachieved is required. On the other hand, in the organic film etching, agas not containing F such as O₂, CO, N₂, or H₂ is used, and an etchingapparatus that enables high-electron-density low-bias etching to beachieved is required.

Meanwhile, in recent years, so that the plasma in the processing spacecan be controlled to be in a desired state, plasma processingapparatuses in which radio frequency electrical power is not supplied tothe upper electrode have been developed. In such a plasma processingapparatus, the upper electrode is electrically insulated from the wallof the substrate processing chamber, and hence the radio frequencyelectrical power supplied to the lower electrode is not supplied intothe upper electrode via the wall, which is grounded. Moreover, the upperelectrode receives charge from the plasma, but there is no outflow ofthe charge from the upper electrode, and hence the upper electrode ischarged up, whereby a potential difference between a surface of theupper electrode and the plasma in the processing space is reduced. Theenergy of ions colliding with the surface of the upper electrode is thusreduced, and hence polymer that has become attached to the surface ofthe upper electrode cannot be removed.

In the case that the polymer attached to the surface of the upperelectrode is not removed, problems arise, for example the polymerdetaches to form particles, which become attached to the front surfaceof wafers, causing a worsening of the yield of semiconductor devicesmanufactured from the wafers.

Moreover, in the case of using, as an etching apparatus that carries outa multi-layer resist process as described above, an apparatus that has asilicon-based upper electrode and in which radio frequency electricalpower is applied into the processing space from each of the upperelectrode and the lower electrode, it is known that if the silicon-basedupper electrode is sputtered in the inorganic film processing, then evenif high-electron-density plasma is used, a high selectivity relative tothe photoresist acting as the mask film can be achieved. However, in theorganic film processing, a problem arises that, upon radio frequencyelectrical power being applied to the upper electrode, the silicon-basedupper electrode material flies off due to sputtering and accumulates onthe wafer. Because the processing gas supplied into the processing spacein the organic film processing is a gas not containing F, thesilicon-based material accumulated on the wafer cannot be removed, butrather accumulates as residue.

In the case that an apparatus in which radio frequency electrical poweris applied from only the lower electrode is used, the above problem doesnot arise. However, in the inorganic film processing, because the effectof the silicon-based upper electrode being sputtered is not obtained, inthe case that high-electron-density plasma is used, a problem of thephotoresist selectivity decreasing arises.

SUMMARY OF THE INVENTION

The present invention provides a plasma processing apparatus, a plasmaprocessing method, and a storage medium, which enable polymer to beremoved from an electrically insulated electrode.

The present invention provides a plasma processing apparatus, a plasmaprocessing method, and a storage medium, which enable a continuousprocess comprising inorganic film processing and organic film processingto be carried out on a substrate.

In a first aspect of the present invention, there is provided a plasmaprocessing apparatus comprising a substrate processing chamber that hastherein a processing space into which a substrate is transferred and isconfigured to carry out plasma processing on the substrate in theprocessing space, a first electrode that is disposed in the substrateprocessing chamber and is connected to a radio frequency power source,and a second electrode that has an exposed portion exposed to theprocessing space and is electrically insulated from the substrateprocessing chamber and the first electrode, wherein the second electrodeis connected to a DC power source.

According to the plasma processing apparatus of the present invention, aDC voltage is applied to the second electrode which has an exposedportion exposed to the processing space and is electrically insulatedfrom the substrate processing chamber and the first electrode. As aresult, a potential difference is produced between plasma in theprocessing space and the exposed portion of the second electrode, andhence ions collide with the exposed portion of the second electrode.Polymer can thus be removed from the electrically insulated secondelectrode.

The plasma processing apparatus can further comprise a controllerconfigured to control a value of a DC voltage applied to the secondelectrode, wherein the controller is configured to determine the valueof the applied DC voltage in accordance with an amount of depositattached to the exposed portion.

In this case, the value of the DC voltage applied to the secondelectrode is determined in accordance with the amount of depositattached to the exposed portion. As a result, polymer can be suitablyremoved from the second electrode.

The plasma processing apparatus can further comprise a controllerconfigured to control a value of a DC voltage applied to the secondelectrode, wherein the controller is configured to determine the valueof the applied DC voltage in accordance with at least one of a type of agas introduced into the processing space, a magnitude of radio frequencyelectrical power supplied to the first electrode, and a pressure in theprocessing space.

In this case, the value of the DC voltage applied to the secondelectrode is determined in accordance with at least one of the type ofthe gas introduced into the processing space, the magnitude of radiofrequency electrical power supplied to the first electrode, and thepressure in the processing space. The amount of deposit attached to theexposed portion of the second electrode is related to the at least oneof the above gas type, the above radio frequency electrical powermagnitude, and the above pressure. As a result, polymer can be suitablyremoved from the second electrode.

The DC power source can apply a DC voltage to the second electrode atleast while the radio frequency power source is supplying radiofrequency electrical power to the first electrode.

In this case, the DC voltage is applied to the second electrode at leastwhile the radio frequency power source is supplying the radio frequencyelectrical power to the first electrode. While the radio frequency powersource is supplying the radio frequency electrical power to the firstelectrode, plasma is produced in the processing space and hence reactionproduct is produced. However, even if this reaction product becomesattached to the exposed portion of the second electrode, the reactionproduct is removed therefrom through collisions with ions due to thepotential difference between the plasma in the processing space and theexposed portion of the second electrode. As a result, polymer can bereliably removed from the second electrode.

The DC power source can apply a DC voltage to the second electrode atleast while plasma is being produced in the processing space.

In this case, the DC voltage is applied to the second electrode at leastwhile the plasma is being produced in the processing space. While theplasma is being produced in the processing space, reaction product isproduced in the processing space. However, even if this reaction productbecomes attached to the exposed portion of the second electrode, thereaction product is removed therefrom through collisions with ions dueto the potential difference between the plasma in the processing spaceand the exposed portion of the second electrode. As a result, polymercan be reliably removed from the second electrode.

In a second aspect of the present invention, there is provided a plasmaprocessing method for a plasma processing apparatus having a substrateprocessing chamber that has therein a processing space into which asubstrate is transferred and is configured to carry out plasmaprocessing on the substrate in the processing space, a first electrodethat is disposed in the substrate processing chamber and is connected toa radio frequency power source, and a second electrode that has anexposed portion exposed to the processing space and is electricallyinsulated from the substrate processing chamber and the first electrode,the method comprising a DC voltage application step of applying a DCvoltage to the second electrode.

The plasma processing method can further comprise a voltage valuedetermining step of determining a value of the DC voltage applied to thesecond electrode in accordance with an amount of deposit attached to theexposed portion.

The plasma processing method can further comprise a voltage valuedetermining step of determining a value of the DC voltage applied to thesecond electrode in accordance with at least one of a type of a gasintroduced into the processing space, a magnitude of radio frequencyelectrical power supplied to the first electrode, and a pressure in theprocessing space

In the DC voltage application step, the DC voltage can be applied to thesecond electrode at least while the radio frequency power source issupplying radio frequency electrical power to the first electrode.

In the DC voltage application step, the DC voltage can be applied to thesecond electrode at least while plasma is being produced in theprocessing space.

In a third aspect of the present invention, there is provided acomputer-readable storage medium storing a program for causing acomputer to implement a plasma processing method for a plasma processingapparatus having a substrate processing chamber that has therein aprocessing space into which a substrate is transferred and is configuredto carry out plasma processing on the substrate in the processing space,a first electrode that is disposed in the substrate processing chamberand is connected to a radio frequency power source, and a secondelectrode that has an exposed portion exposed to the processing spaceand is electrically insulated from the substrate processing chamber andthe first electrode, the method comprising a DC voltage application stepof applying a DC voltage to the second electrode.

In a fourth aspect of the present invention, there is provided a plasmaprocessing apparatus comprising a substrate processing chamber that hastherein a processing space into which a substrate is transferred and isconfigured to carry out plasma processing on the substrate in theprocessing space, a first electrode that is disposed in the substrateprocessing chamber and is connected to a radio frequency power source,and a second electrode that has an exposed portion exposed to theprocessing space and is electrically insulated from the substrateprocessing chamber and the first electrode, wherein the substrate has aninorganic film and an organic film formed thereon, wherein when plasmaprocessing is being carried out on the inorganic film on the substrate,a potential difference between the processing space and the secondelectrode is set to a value at which the exposed portion of the secondelectrode is sputtered by plasma produced in the processing space, andwherein when plasma processing is being carried out on the organic filmon the substrate, the potential difference between the processing spaceand the second electrode is set to a value lower than the value of thepotential difference for when the plasma processing is being carried outon the inorganic film.

According to this plasma processing apparatus, when plasma processing isbeing carried out on the inorganic film on the substrate having theinorganic film and the organic film formed thereon, the potentialdifference between the processing space and the second electrode is setto a value at which the exposed portion of the second electrode issputtered by plasma produced in the processing space, and when plasmaprocessing is being carried out on the organic film on the substrate,the potential difference between the processing space and the secondelectrode is set to a value lower than the value of the potentialdifference for when the plasma processing is being carried out on theinorganic film. As a result, in the inorganic film processing, theexposed portion of the second electrode is sputtered, whereby highselectivity relative to a resist film can be secured in etching of theinorganic film. On the other hand, in the organic film processing, thepotential difference between the plasma in the processing space and theexposed portion of the second electrode is reduced, and hence theexposed portion of the second electrode is not sputtered, wherebyresidue can be prevented from being produced on the substrate in etchingof the organic film. An inorganic film processing process and an organicfilm processing process can thus be carried out on the substrate as acontinuous process in the same plasma processing apparatus.

The second electrode can be connected to a DC power source.

In this case, the second electrode is connected to a DC power source. Asa result, the potential difference between the plasma in the processingspace and the exposed portion of the second electrode can be reliablyset to a desired potential.

The plasma processing apparatus can further comprise a switching devicedisposed between the second electrode and the DC power source, whereinwhen the plasma processing is being carried out on the organic film onthe substrate, the switching device cuts off electrical connectionbetween the second electrode and the DC power source so as toelectrically insulate the second electrode.

In this case, when the plasma processing is being carried out on theorganic film on the substrate, electrical connection between the secondelectrode and the DC power source is cut off so as to electricallyinsulate the second electrode. As a result, the potential differencebetween the plasma in the processing space and the exposed portion ofthe second electrode can be reliably made to be lower than the potentialdifference for when the plasma processing is being carried out on theinorganic film.

The second electrode can be grounded when the plasma processing is beingcarried out on the inorganic film on the substrate.

In this case, when the plasma processing is being carried out on theinorganic film on the substrate, the second electrode is grounded. As aresult, the potential difference between the plasma in the processingspace and the exposed portion of the second electrode can be easily setto a value at which the exposed portion of the second electrode issputtered.

Radio frequency electrical power of frequency not more than 27 MHz thatproduces a desired DC voltage can be applied to the second electrodewhen the plasma processing is being carried out on the inorganic film onthe substrate.

In this case, when the plasma processing is being carried out on theinorganic film on the substrate, radio frequency electrical power offrequency not more than 27 MHz that produces a desired DC voltage isapplied to the second electrode. As a result, the potential differencebetween the plasma in the processing space and the exposed portion ofthe second electrode can be reliably set to a value at which the exposedportion of the second electrode is sputtered.

The second electrode can be electrically insulated when the plasmaprocessing is being carried out on the organic film on the substrate.

In this case, when the plasma processing is being carried out on theorganic film on the substrate, the second electrode is electricallyinsulated. As a result, the exposed portion of the second electrodereceives charge from the plasma in the processing space, but there is nooutflow of the charge from the exposed portion, and hence the exposedportion is charged up. The potential difference between the plasma inthe processing space and the exposed portion of the second electrode canthus be reliably reduced.

The exposed portion can comprise a silicon-based material.

In this case, the exposed portion of the second electrode comprises asilicon-based material. As a result, when the exposed portion of thesecond electrode is sputtered during the inorganic film processing, highselectivity relative to a resist film can be secured in the etching ofthe inorganic film.

In a fifth aspect of the present invention, there is provided a plasmaprocessing method for a plasma processing apparatus having a substrateprocessing chamber that has therein a processing space into which asubstrate is transferred and is configured to carry out plasmaprocessing on the substrate in the processing space, a first electrodethat is disposed in the substrate processing chamber and is connected toa radio frequency power source, and a second electrode that has anexposed portion exposed to the processing space and is electricallyinsulated from the substrate processing chamber and the first electrode,the substrate having an inorganic film and an organic film formedthereon, the method comprising an inorganic film processing step ofcarrying out plasma processing on the inorganic film on the substrate,and an organic film processing step of carrying out plasma processing onthe organic film on the substrate, wherein in the inorganic filmprocessing step, a potential difference between the processing space andthe second electrode is set to a value at which the exposed portion ofthe second electrode is sputtered by plasma produced in the processingspace, and in the organic film processing step, the potential differencebetween the processing space and the second electrode is set to a valuelower than the value of the potential difference for when the plasmaprocessing is being carried out on the inorganic film.

The plasma processing method can further comprise a DC power sourceconnection step of connecting a DC power source to the second electrode.

In the inorganic film processing step, the second electrode can begrounded.

In the inorganic film processing step, radio frequency electrical powerof frequency not more than 27 MHz that produces a desired DC voltage canbe applied to the second electrode.

In the organic film processing step, the second electrode can beelectrically insulated.

The exposed portion can comprise a silicon-based material.

In a sixth aspect of the present invention, there is provided acomputer-readable storage medium storing a program for causing acomputer to implement a plasma processing method for a plasma processingapparatus having a substrate processing chamber that has therein aprocessing space into which a substrate is transferred and is configuredto carry out plasma processing on the substrate in the processing space,a first electrode that is disposed in the substrate processing chamberand is connected to a radio frequency power source, and a secondelectrode that has an exposed portion exposed to the processing spaceand is electrically insulated from the substrate processing chamber andthe first electrode, the substrate having an inorganic film and anorganic film formed thereon, the method comprising an inorganic filmprocessing step of carrying out plasma processing on the inorganic filmon the substrate, and an organic film processing step of carrying outplasma processing on the organic film on the substrate, wherein in theinorganic film processing step, a potential difference between theprocessing space and the second electrode is set to a value at which theexposed portion of the second electrode is sputtered by plasma producedin the processing space, and in the organic film processing step, thepotential difference between the processing space and the secondelectrode is set to a value lower than the value of the potentialdifference for when the plasma processing is being carried out on theinorganic film.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view schematically showing the construction of aplasma processing apparatus according to a first embodiment of thepresent invention;

FIG. 2 is a graph showing the relationship between processing conditionsand a deposit film thickness on a lower surface of an upper electrodeplate;

FIG. 3 is a flowchart of a plasma processing method according to thefirst embodiment of the present invention;

FIG. 4 is a sectional view schematically showing the construction of aplasma processing apparatus according to a second embodiment of thepresent invention;

FIG. 5 is a sectional view schematically showing the cross-sectionalform of a wafer to be processed by the plasma processing apparatus shownin FIG. 4;

FIG. 6 is a flowchart of a plasma processing method according to thesecond embodiment of the present invention;

FIG. 7 is a flowchart showing a procedure for an inorganic filmprocessing process of each of steps S62 and S64 appearing in FIG. 6; and

FIG. 8 is a flowchart showing a procedure for an organic film processingprocess of step S63 appearing in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail below withreference to the drawings showing preferred embodiments thereof.

FIG. 1 is a sectional view schematically showing the construction of aplasma processing apparatus according to a first embodiment of thepresent invention. The plasma processing apparatus is constructed suchas to carry out RIE (reactive ion etching) processing or ashingprocessing on a semiconductor wafer W as a substrate.

As shown in FIG. 1, the plasma processing apparatus 10 has a cylindricalsubstrate processing chamber 11, the substrate processing chamber 11having a processing space S therein. A cylindrical susceptor 12 (firstelectrode) is disposed in the substrate processing chamber 11 as a stageon which is mounted a semiconductor wafer W (hereinafter referred tomerely as a “wafer W”) having a diameter of, for example, 300 mm. Aninner wall surface of the substrate processing chamber 11 is coveredwith a side wall member 45. The side wall member 45 is made of aluminum,a surface thereof facing the processing space S being coated with yttria(Y₂O₃). Moreover, the substrate processing chamber 11 is electricallygrounded, so that the side wall member 45 is at ground potential. Thesusceptor 12 is installed via an insulating member 29 on a bottomportion of the substrate processing chamber 11. A side face of thesusceptor 12 is covered with a susceptor side face covering member 50.

In the plasma processing apparatus 10, an exhaust path 13 that acts as aflow path through which gas molecules above the susceptor 12 areexhausted out of the substrate processing chamber 11 is formed betweenan inner side wall of the substrate processing chamber 11 and the sideface of the susceptor 12. An annular exhaust plate 14 that preventsleakage of plasma is disposed part way along the exhaust path 13. Aspace in the exhaust path 13 downstream of the exhaust plate 14 bendsround below the susceptor 12, and is communicated with an automaticpressure control valve (hereinafter referred to as the “APC valve”) 15,which is a variable butterfly valve. The APC valve 15 is connected viaan isolator 16 to a turbo-molecular pump (hereinafter referred to as the“TMP”) 17, which is an exhausting pump for evacuation. The TMP 17 isconnected via a valve V1 to a dry pump (hereinafter referred to as the“DP”) 18, which is also an exhausting pump. The exhaust flow pathcomprised of the APC valve 15, the isolator 16, the TMP 17, the valveV1, and the DP 18 is used for controlling the pressure in the substrateprocessing chamber 11, more specifically the processing space S, usingthe APC valve 15, and also for reducing the pressure in the substrateprocessing chamber 11 down to a substantially vacuum state using the TMP17 and the DP 18.

Moreover, piping 19 is connected from between the isolator 16 and theAPC valve 15 to the DP 18 via a valve V2. The piping 19 and the valve V2bypass the TMP 17, and are used for roughing the substrate processingchamber 11 using the DP 18.

A radio frequency power source 20 is connected to the susceptor 12 via afeeder rod 21 and a matcher 22. The radio frequency power source 20supplies radio frequency electrical power of a relatively highfrequency, for example 40 MHz, to the susceptor 12. The susceptor 12thus acts as a lower electrode. The matcher 22 reduces reflection of theradio frequency electrical power from the susceptor 12 so as to maximizethe efficiency of the supply of the radio frequency electrical powerinto the susceptor 12. The susceptor 12 applies into the processingspace S the 40 MHz radio frequency electrical power supplied from theradio frequency power source 20.

Moreover, another radio frequency power source 46 is connected to thesusceptor 12 via a feeder rod 35 and a matcher 36. The other radiofrequency power source 46 supplies radio frequency electrical power of afrequency lower than that of the radio frequency electrical powersupplied by the radio frequency power source 20, for example 3.13 MHz,to the susceptor 12. The matcher 36 has a similar function to thematcher 22.

A radio frequency (3.13 MHz) potential arises on a surface of thesusceptor 12 and a surface of the susceptor side face covering member 50due to the supplied 3.13 MHz radio frequency electrical power. Apotential that fluctuates at 3.13 MHz thus arises on the surface of thesusceptor 12 and the surface of the susceptor side face covering member50, and hence of positive ions in the plasma produced in the processingspace S, positive ions corresponding in number to a potential differencebetween the plasma in the processing space S and the surface of thesusceptor 12 collides with the surface of the susceptor 12, and likewisefor the susceptor side face covering member 50. Polymer that has becomeattached to the surface of the susceptor 12 and the surface of thesusceptor side face covering member 50 is removed through collisionswith the positive ions (sputtering). Furthermore, a potential due to the40 MHz radio frequency electrical power also arises on the surface ofthe susceptor 12 and the surface of the susceptor side face coveringmember 50, but positive ions cannot follow a potential differencefluctuating at 40 MHz, and hence the potential difference produced dueto the 40 MHz radio frequency electrical power is small, and thus theenergy of positive ions colliding with the surface of the susceptor 12and the surface of the susceptor side face covering member 50 is low.

A disk-shaped ESC electrode plate 23 comprised of an electricallyconductive film is provided in an upper portion of the susceptor 12. AnESC DC power source 24 is electrically connected to the ESC electrodeplate 23. A wafer W is attracted to and held on an upper surface of thesusceptor 12 through a Johnsen-Rahbek force or a Coulomb force generatedby a DC voltage applied to the ESC electrode plate 23 from the ESC DCpower source 24. Moreover, an annular focus ring 25 is provided on anupper portion of the susceptor 12 so as to surround the wafer Wattracted to and held on the upper surface of the susceptor 12. Thefocus ring 25 is exposed to the processing space S, and focuses plasmain the processing space S toward a front surface of the wafer W, thusimproving the efficiency of the RIE processing or ashing processing.

An annular coolant chamber 26 that extends, for example, in acircumferential direction of the susceptor 12 is provided inside thesusceptor 12. A coolant, for example cooling water or a Galden(registered trademark) fluid, at a predetermined temperature iscirculated through the coolant chamber 26 via coolant piping 27 from achiller unit (not shown). A processing temperature of the wafer Wattracted to and held on the upper surface of the susceptor 12 iscontrolled through the temperature of the coolant.

A plurality of heat-transmitting gas supply holes 28 are opened to aportion of the upper surface of the susceptor 12 on which the wafer W isattracted and held (hereinafter referred to as the “attractingsurface”). The heat-transmitting gas supply holes 28 are connected to aheat-transmitting gas supply unit 32 by a heat-transmitting gas supplyline 30 provided inside the susceptor 12. The heat-transmitting gassupply unit 32 supplies helium gas as a heat-transmitting gas via theheat-transmitting gas supply holes 28 into a gap between the attractingsurface of the susceptor 12 and a rear surface of the wafer W.

A plurality of pusher pins 33 are provided in the attracting surface ofthe susceptor 12 as lifting pins that can be made to project out fromthe upper surface of the susceptor 12. The pusher pins 33 are connectedto a motor (not shown) by a ball screw (not shown), and can be made toproject out from the attracting surface of the susceptor 12 throughrotational motion of the motor, which is converted into linear motion bythe ball screw. The pusher pins 33 are housed inside the susceptor 12when a wafer W is being attracted to and held on the attracting surfaceof the susceptor 12 so that the wafer W can be subjected to the RIEprocessing or ashing processing, and are made to project out from theupper surface of the susceptor 12 so as to lift the wafer W up away fromthe susceptor 12 when the wafer W is to be transferred out from thesubstrate processing chamber 11 after having been subjected to the RIEprocessing or ashing processing.

A gas introducing shower head 34 is disposed in a ceiling portion of thesubstrate processing chamber 11 such as to face the susceptor 12. Thegas introducing shower head 34 is comprised of an electrode platesupport 39 made of an electrically conductive material having a bufferchamber 40 formed therein, and an upper electrode plate 38 (secondelectrode) which is supported by the electrode plate support 39. A lowersurface (exposed portion) of the upper electrode plate 38 is exposed tothe processing space S. The upper electrode plate 38 is a disk-shapedmember made of a silicon-based electrically conductive material, forexample Si or SiC. A peripheral portion of the upper electrode plate 38and a peripheral portion of the electrode plate support 39 are coveredwith an annular insulating member 47 made of an insulating material.That is, the upper electrode plate 38 and the electrode plate support 39are electrically insulated by the insulating member 47 from the wall ofthe substrate processing chamber 11 which is at ground potential, andfrom the susceptor 12 to which radio frequency electrical power issupplied.

A processing gas introducing pipe 41 is connected from a processing gassupply unit (not shown) to the buffer chamber 40 in the electrode platesupport 39. A piping insulator 42 is disposed part way along theprocessing gas introducing pipe 41. Moreover, the gas introducing showerhead 34 has therein a plurality of gas holes 37 that communicate thebuffer chamber 40 to the processing space S. A processing gas suppliedfrom the processing gas introducing pipe 41 into the buffer chamber 40is supplied by the gas introducing shower head 34 into the processingspace S via the gas holes 37.

The upper electrode plate 38 is electrically connected to a DC powersource 49 via a radio frequency filter 51. The DC power source 49applies a negative DC voltage to the upper electrode plate 38. The valueof the DC voltage applied to the upper electrode plate 38 by the DCpower source 49 is determined by a controller 52, described below.

A transfer port 43 for the wafers W is provided in the side wall of thesubstrate processing chamber 11 in a position at the height of a wafer Wthat has been lifted up from the susceptor 12 by the pusher pins 33. Agate valve 44 for opening and closing the transfer port 43 is providedin the transfer port 43.

In the substrate processing chamber 11 of the plasma processingapparatus 10, through the susceptor 12 applying radio frequencyelectrical power into the processing space S which is the space betweenthe susceptor 12 and the upper electrode plate 38 as described above,the processing gas supplied from the gas introducing shower head 34 intothe processing space S is turned into high-density plasma so thatpositive ions and radicals are produced, whereby the wafer W issubjected to the RIE processing or ashing processing by the positiveions and radicals.

Moreover, the plasma processing apparatus 10 further has the controller52, which controls operation of component elements of the plasmaprocessing apparatus 10, a database 53 in which various types of dataare stored, and an input section, for example an operation panel (notshown) for an operator to input processing conditions and so on.

When a wafer W is subjected to RIE processing in the plasma processingapparatus 10 described above, if a deposit-producing processing gas suchas a mixed gas of C₄F₈ gas and argon gas is used, then reaction productproduced from the processing gas becomes attached as polymer to thelower surface of the upper electrode plate 38, the surface of thesusceptor 12, the surface of the side wall member 45, and the surface ofthe susceptor side face covering member 50. The attached polymer forms adeposit film on each of these surfaces. Here, the polymer attached tothe surface of the susceptor 12 and the surface of the susceptor sideface covering member 50 is removed through collisions with positive ionsas described earlier. Moreover, the side wall member 45 is at groundpotential, and hence positive ions also collide with the side wallmember 45. The polymer attached to the surface of the side wall member45 is thus also removed. However, in the case that a DC voltage is notapplied to the upper electrode plate 38, because the upper electrodeplate 38 is electrically insulated, a potential difference between thelower surface of the upper electrode plate 38 and the plasma in theprocessing space S is reduced, and hence ions do not collide with thelower surface of the upper electrode plate 38, and thus the polymerattached to the lower surface of the upper electrode plate 38 is notremoved.

In the present embodiment, a potential difference is thus producedbetween the lower surface of the upper electrode plate 38 and the plasmain the processing space S so that polymer attached to the lower surfaceof the upper electrode plate 38 is removed through collisions withpositive ions. Specifically, the DC power source 49 applies a negativeDC voltage to the upper electrode plate 38.

To investigate what value of negative DC voltage to apply to the upperelectrode plate 38, the present inventors first produced plasma from theprocessing gas in the processing space S without applying a DC voltageto the upper electrode plate 38 in the plasma processing apparatus 10,whereupon it was ascertained that the amount of polymer becomingattached to the lower surface of the upper electrode plate 38 changes inaccordance with at least one of the processing conditions for the RIEprocessing, for example the type of the processing gas introduced intothe processing space S, the magnitude of the radio frequency electricalpower supplied to the susceptor 12, and the pressure in the processingspace S. Specifically, the present inventors ascertained that thedeposit film thickness on the lower surface of the upper electrode plate38 changes upon changing the processing conditions (conditions A to H)(FIG. 2). This is because if a processing condition is changed,specifically the pressure in the processing space S and/or the magnitudeof the radio frequency electrical power is changed, then the potentialdifference between the lower surface of the upper electrode plate 38 andthe plasma in the processing space S changes accordingly.

As described above, the deposit film thickness on the lower surface ofthe upper electrode plate 38 changes in accordance with the processingconditions for the RIE processing. In the present embodiment, the valueof the negative DC voltage to be applied to the upper electrode plate 38is thus determined in accordance with the processing conditions.Specifically, the deposit film thickness under each set of processingconditions in the plasma processing apparatus 10 is measured in advance,and the relationship between the processing conditions and the depositfilm thickness (hereinafter referred to as the “processingcondition-deposit film thickness relationship”) is stored in thedatabase 53; furthermore, for each of a plurality of deposit filmthicknesses, the value of the negative DC voltage at which the depositfilm can be removed but the upper electrode plate 38 itself is notsputtered is determined using the plasma processing apparatus 10, andthe relationship between the thickness of the deposit film to be removedand the required value of the negative DC voltage (hereinafter referredto as the “deposit film thickness-DC voltage value relationship”) isalso stored in the database 53. The controller 52 then determines thevalue of the negative DC voltage to be applied to the upper electrodeplate 38 from the processing conditions for the RIE processing to becarried out, based on the processing condition-deposit film thicknessrelationship and the deposit film thickness-DC voltage valuerelationship stored in the database 53.

Next, a plasma processing method according to the first embodiment ofthe present invention will be described.

FIG. 3 is a flowchart of the plasma processing method according to thefirst embodiment of the present invention.

As shown in FIG. 3, first, upon the operator using the operation panelto input the processing conditions, for example a desired processing gastype, radio frequency electrical power magnitude, and processing space Spressure, for the RIE processing to be carried out by the plasmaprocessing apparatus 10, the controller 52 determines the value of thenegative DC voltage to be applied to the upper electrode plate 38 fromat least one of the desired processing gas type, radio frequencyelectrical power magnitude, and processing space S pressure, based onthe processing condition-deposit film thickness relationship and thedeposit film thickness-DC voltage value relationship stored in thedatabase 53 (step S31) (voltage value determining step).

Next, a wafer W is transferred into the substrate processing chamber 11(step S32), the wafer W is attracted to and held on the attractingsurface of the susceptor 12, and the pressure in the substrateprocessing chamber 11 is reduced to the pressure in the inputtedprocessing conditions, and then the DC power source 49 starts to apply anegative DC voltage of the determined value to the upper electrode plate38 (step S33) (DC voltage application step), the gas introducing showerhead 34 supplies the processing gas into the processing space S (stepS34), and the radio frequency power source 20 and the other radiofrequency power source 46 supply 40 MHz and 3.13 MHz radio frequencyelectrical power respectively to the susceptor 12, so that the susceptor12 starts to apply 40 MHz and 3.13 MHz radio frequency electrical powerinto the processing space S (step S35). At this time, the processing gasis turned into high-density plasma, so that positive ions and radicalsare produced in the processing space S. The wafer W is subjected to RIEprocessing by the positive ions and radicals (step S36).

While the plasma is being produced in the processing space S, reactionproduct is produced from the processing gas and becomes attached aspolymer to the lower surface of the upper electrode plate 38. However,because the negative DC voltage is being applied to the upper electrodeplate 38, a potential difference arises between the lower surface of theupper electrode plate 38 and the plasma in the processing space S, sothat positive ions collide with the lower surface of the upper electrodeplate 38. As a result, the polymer attached to the lower surface of theupper electrode plate 38 is removed.

Upon the RIE processing on the wafer W being completed, the supply ofthe radio frequency electrical power to the susceptor 12 by each of theradio frequency power source 20 and the other radio frequency powersource 46 is stopped, so that the application of the radio frequencyelectrical power into the processing space S is stopped (step S37). Atthis time, the plasma in the processing space S disappears.

Next, the application of the negative DC voltage to the upper electrodeplate 38 by the DC power source 49 is stopped (step S38), the pressurein the substrate processing chamber 11 is raised to atmosphericpressure, and the wafer W that has been subjected to the RIE processingis transferred out from the substrate processing chamber 11 (step S39),whereupon the present process comes to an end.

According to the process of FIG. 3 described above, a negative DCvoltage is applied to the upper electrode plate 38, which iselectrically insulated. As a result, a potential difference is producedbetween the plasma in the processing space S and the lower surface ofthe upper electrode plate 38, and hence positive ions collide with thelower surface of the upper electrode plate 38. Polymer can thus beremoved from the lower surface of the upper electrode plate 38.

In the process of FIG. 3, the value of the negative DC voltage to beapplied to the upper electrode plate 38 is determined from at least oneof the type of the gas to be introduced into the processing space S, themagnitude of the radio frequency electrical power to be supplied to thesusceptor 12, and the pressure in the processing space S, based on theprocessing condition-deposit film thickness relationship and the depositfilm thickness-DC voltage value relationship stored in the database 53.The deposit film thickness on the lower surface of the upper electrodeplate 38 is related to the at least one of the above gas type, the aboveradio frequency electrical power magnitude, and the above pressure.Moreover, the value of the negative DC voltage in the deposit filmthickness-DC voltage value relationship stored in the database 53 is anegative DC voltage value at which the deposit film can be removed butthe upper electrode plate 38 itself is not sputtered. As a result, theamount of sputtering by positive ions colliding with the lower surfaceof the upper electrode plate 38 can be suitably controlled, and hencethe polymer can be suitably removed from the upper electrode plate 38,and yet wear of the upper electrode plate 38 can be prevented.

Moreover, in the process of FIG. 3, the negative DC voltage is appliedto the upper electrode plate 38 while the radio frequency electricalpower is being supplied to the susceptor 12 by the radio frequency powersource 20 and the other radio frequency power source 46. While the radiofrequency electrical power is being supplied to the susceptor 12, plasmais produced in the processing space S, and hence reaction product isproduced from the processing gas and becomes attached as polymer to thelower surface of the upper electrode plate 38. However, because thenegative DC voltage is being applied to the upper electrode plate 38,the polymer is removed through collisions with positive ions. As aresult, the polymer can be reliably removed from the upper electrodeplate 38.

In the process of FIG. 3 described above, the absolute value of thenegative DC voltage applied to the upper electrode plate 38 ispreferably in a range of 0 V to 2000 V, which is a value such as not toaffect the plasma, more preferably 50 V to 200 V.

Note that the negative DC voltage applied to the upper electrode plate38 may also be used to control the plasma distribution or the like, inwhich case the value of the negative DC voltage is not limited to beingas above.

In the present embodiment described above, polymer attached to the lowersurface of the upper electrode plate 38 is removed through theapplication of the negative DC voltage. However, the object of removalis not limited to this. For example, an oxide film formed on the lowersurface of the upper electrode plate 38 may also be removed through theapplication of the negative DC voltage.

Moreover, in the present embodiment described above, the value of thenegative DC voltage to be applied is determined in accordance with theprocessing conditions for the RIE processing to be carried out on thewafer W before the RIE processing is carried out. However, the value ofthe negative DC voltage may also be changed as appropriate during theRIE processing in accordance with the luminescence of the plasma in theprocessing space S or the amount of polymer attached to the lowersurface of the upper electrode plate 38. An example of a method ofmeasuring the amount of polymer attached to the lower surface of theupper electrode plate 38 is a method in which part of an optical fiberhaving both ends thereof disposed outside the substrate processingchamber 11 is exposed to the interior of the substrate processingchamber 11, and the transmissivity of the optical fiber is monitored.The transmissivity of the optical fiber changes upon polymer becomingattached to the optical fiber, and hence the amount of polymer attachedto the lower surface of the upper electrode plate 38 can be measuredusing this method.

In the present embodiment described above, the plasma processingapparatus 10 has the controller 52 and the database 53. However, anexternal server and database connected to the plasma processingapparatus 10 may alternatively serve these functions.

Next, a plasma processing apparatus according to a second embodiment ofthe present invention will be described.

The present embodiment is basically the same as the first embodimentdescribed above in terms of construction and operation, differing fromthe first embodiment in that there is a switch between the DC powersource and the radio frequency filter. Features of the construction andoperation that are the same as in the first embodiment will thus not bedescribed, only features that are different from those of the firstembodiment being described below.

FIG. 4 is a sectional view schematically showing the construction of theplasma processing apparatus according to the second embodiment.

As shown in FIG. 4, the plasma processing apparatus 55 has a switch 54(switching device) disposed between the DC power source 49 and the radiofrequency filter 51.

When the switch 54 is on, the upper electrode plate 38 is electricallyconnected to the DC power source 49 via the radio frequency filter 51,so that the DC power source 49 applies a DC voltage to the upperelectrode plate 38. The value of the DC voltage applied to the upperelectrode plate 38 by the DC power source 49 is determined by thecontroller 52. When the switch 54 is off, the upper electrode plate 38is electrically “floating”. The switching on and off of the switch 54 iscontrolled by the controller 52 as described below.

FIG. 5 is a sectional view schematically showing the cross-sectionalform of a wafer W to be processed by the plasma processing apparatus 55shown in FIG. 4. In the present embodiment, the case that a multi-layerresist film is formed on the wafer W is described.

As shown in FIG. 5, the multi-layer resist film on the wafer W is firstproduced by forming, on an SiO₂ film 62 (inorganic film) to be processedthat has been formed on an Si substrate 61, an amorphous carbon film 63(organic film) that can be selectively etched relative to the SiO₂ film62, an SOG film 64 (inorganic film) that can be selectively etchedrelative to the amorphous carbon film 63, and a resist film 65 in thisorder. The SOG film 64 is, for example, made of SiO₂ or SiOC.

In the present embodiment, a processing process is carried outcontinuously in a single chamber on the wafer W on which the multi-layerresist film has been formed as described above. Specifically, the resistfilm 65 is patterned by photolithography, and the SOG film 64 is etchedusing the resist film 65 as a mask, thus transferring the pattern of theresist film 65 onto the SOG film 64. Next, the amorphous carbon film 63is etched using the patterned SOG film 64 as a mask, thus transferringthe pattern of the SOG film 64 onto the amorphous carbon film 63.Processing of the SiO₂ film 62 that is the object of the processing isthen carried out using the patterned amorphous carbon film 63 as a mask.

More specifically, in each of the etching of the SOG film 64 and theetching of the SiO₂ film 62, the pressure in the substrate processingchamber 11 into which the wafer W has been transferred is set to apressure in processing conditions that have been inputted using theoperation panel or the like, a DC voltage of a value determined based onthe inputted processing conditions is applied to the upper electrodeplate 38, a CF type processing gas such as C₄F₈ is supplied into theprocessing space S from the gas introducing shower head 34, and 40 MHzradio frequency electrical power and 3.13 MHz radio frequency electricalpower supplied to the susceptor 12 from the radio frequency power source20 and the other radio frequency power source 46 respectively areapplied into the processing space S, so as to turn the suppliedprocessing gas into high-density plasma, whereby positive ions andradicals are produced, the wafer W being subjected to RIE processing bythe positive ions and radicals.

On the other hand, in the etching of the amorphous carbon film 63, theswitch 54 is turned off based on the inputted processing conditions soas to put the upper electrode plate 38 into a floating state, and thepressure in the substrate processing chamber 11 into which the wafer Whas been transferred is set to a pressure in the inputted processingconditions, and then a processing gas not containing F such as O₂, CO,N₂, or H₂ is supplied into the processing space S from the gasintroducing shower head 34, and radio frequency electrical power offrequency not less than 40 MHz supplied to the susceptor 12 from theradio frequency power source 20 is applied into the processing space S,so as to turn the supplied processing gas into high-density plasma,whereby positive ions and radicals are produced, the wafer W beingsubjected to RIE processing by the positive ions and radicals.

Next, a plasma processing method according to the second embodiment ofthe present invention will be described.

FIG. 6 is a flowchart of the plasma processing method according to thesecond embodiment of the present invention.

In the plasma processing method of FIG. 6, first, the operator uses theoperation panel to input processing conditions, for example desiredprocessing gas type, radio frequency electrical power magnitude, andprocessing space S pressure, for the RIE processing to be carried out bythe plasma processing apparatus 55.

Next, a wafer W is transferred into the substrate processing chamber 11(step S61), and the wafer W is attracted to and held on the attractingsurface of the susceptor 12, then an inorganic film processing process(step S62), an organic film processing process (step S63), and aninorganic film processing process (step S64), described in detail below,are carried out in this order, and then the pressure in the substrateprocessing chamber 11 is raised to atmospheric pressure, and the wafer Wthat has been subjected to the RIE processing in the respectiveprocessing processes is transferred out from the substrate processingchamber 11 (step S65), whereupon the present process comes to an end.

In the inorganic film processing process of step S62 (inorganic filmprocessing step), the SOG film 64 is etched, and at this time thepattern of the resist film 65 is transferred onto the SOG film 64. Inthe organic film processing process of step S63 (organic film processingstep) the amorphous carbon film 63 is etched, the pattern of the SOGfilm 64 being transferred onto the amorphous carbon film 63. In theinorganic film processing process of step S64 (inorganic film processingstep), the SiO₂ film 62 is etched, and at this time the patternedamorphous carbon film 63 acts as a mask. As a result, an SiO₂ film 62patterned in a desired pattern can be obtained.

FIG. 7 is a flowchart showing a procedure for the inorganic filmprocessing process of each of steps S62 and S64 appearing in FIG. 6.

As shown in FIG. 7, first, the controller 52 determines the value of theDC voltage to be applied to the upper electrode plate 38 based on theprocessing conditions for the RIE processing inputted by the operator(step S71).

Next, the pressure in the substrate processing chamber 11 into which thewafer W has been transferred is reduced or raised to the pressure in theinputted processing conditions, the controller 52 turns the switch 54on, and the DC power source 49 starts to apply a DC voltage of thedetermined value to the upper electrode plate 38 (step S72) (DC powersource connection step). Next, the gas introducing shower head 34supplies a CF type processing gas such as C₄F₈ into the processing spaceS (step S73), and the radio frequency power source 20 and the otherradio frequency power source 46 supply 40 MHz and 3.13 MHz radiofrequency electrical power respectively to the susceptor 12, so that thesusceptor 12 starts to apply 40 MHz and 3.13 MHz radio frequencyelectrical power into the processing space S (step S74). At this time,the processing gas is turned into high-density plasma, so that positiveions and radicals are produced in the processing space S. The wafer W issubjected to RIE processing by the positive ions and radicals (stepS75).

In step S75, because the DC voltage is being applied to the upperelectrode plate 38, a potential difference arises between the lowersurface of the upper electrode plate 38 and the plasma in the processingspace S. Positive ions are drawn onto the upper electrode plate 38 dueto the potential difference, whereby the upper electrode plate 38 issputtered. As described earlier, if such an electrode plate made of asilicon-based material is sputtered, then high selectivity of aninorganic film relative to a mask film can be achieved in the inorganicfilm processing. Accordingly, in step S75, a high selectivity relativeto the resist film 65 can be secured in the etching of the SOG film 64,and a high selectivity relative to the amorphous carbon film 63 can besecured in the etching of the SiO₂ film 62.

It is difficult to clearly explain the mechanism of the effect due tothe sputtering of the electrode plate made of the silicon-basedmaterial, but as a result of carrying out assiduous studies, the presentinventors have come up with the two hypotheses described below.

(1) Through the sputtering of the electrode plate made of thesilicon-based material, the silicon-based material files off and thusaccumulates on the mask film. After that, even if positive ions andradicals from the plasma reach the mask film, these positive ions andradicals are consumed in etching of the accumulated silicon-basedmaterial, and hence the mask film is hardly etched.

(2) In etching by a CF type gas plasma, CF type deposit is produced asreaction product and accumulates on the mask film, thus forming adeposit film. Moreover, during the sputtering of the electrode plate,fluorine ions and fluorine radicals from the CF type gas are consumed.The CF type deposit produced is thus carbon rich. Due to being carbonrich, the deposit film is strengthened and thus becomes less easilyetched. As a result, the deposit film protects the mask film, and hencethe mask film is hardly etched.

Next, upon the RIE processing on the wafer W being completed, the supplyof the radio frequency electrical power to the susceptor 12 by each ofthe radio frequency power source 20 and the other radio frequency powersource 46 is stopped, so that the application of the radio frequencyelectrical power into the processing space S is stopped (step S76). Atthis time, the plasma in the processing space S disappears.

Next, the application of the DC voltage to the upper electrode plate 38by the DC power source 49 is stopped (step S77), whereupon the presentprocess comes to an end.

According to the inorganic film processing process of FIG. 7, a DCvoltage is applied to the upper electrode plate 38. As a result, apotential difference is produced between the plasma in the processingspace S and the lower surface of the upper electrode plate 38, and hencepositive ions collide with the lower surface of the upper electrodeplate 38. That is, the upper electrode plate 38 is sputtered, and hencea high selectivity relative to the resist film 65 can be secured in theetching of the SOG film 64, and a high selectivity relative to theamorphous carbon film 63 can be secured in the etching of the SiO₂ film62.

In the present embodiment, an arrangement in which a DC voltage isapplied to the upper electrode plate 38 is adopted. However, anarrangement in which the upper electrode plate 38 is switched from afloating state to a grounded state may be adopted, or an arrangement inwhich radio frequency electrical power of frequency not more than 27 MHzable to produce a high DC voltage (Vdc) is applied to the upperelectrode plate 38 may be adopted.

FIG. 8 is a flowchart showing a procedure for the organic filmprocessing process of step S63 appearing in FIG. 6.

As shown in FIG. 8, first, based on the processing conditions for theRIE processing inputted by the operator, the controller 52 turns theswitch 54 off, thus putting the upper electrode plate 38 into a floatingstate (step S81).

Next, the pressure in the substrate processing chamber 11 is reduced orraised to the pressure in the inputted processing conditions, the gasintroducing shower head 34 supplies a processing gas not containing Fsuch as O₂, CO, N₂, or H₂ into the processing space S (step S82), andthe radio frequency power source 20 supplies radio frequency electricalpower of frequency not less than 40 MHz to the susceptor 12, so that thesusceptor 12 starts to apply radio frequency electrical power offrequency not less than 40 MHz into the processing space S (step S83).At this time, the processing gas is turned into high-density plasma, sothat positive ions and radicals are produced in the processing space S.The wafer W is subjected to RIE processing by the positive ions andradicals (step S84).

In the present process, because the processing gas supplied into theprocessing space S is a gas not containing F, while the plasma is beingproduced in the processing space S, reaction product is not producedfrom the processing gas, and hence polymer is not attached to the lowersurface of the upper electrode plate 38.

Furthermore, because the upper electrode plate 38 is in a floatingstate, the upper electrode plate 38 receives charge from the plasma inthe processing space S, and there is no outflow of the charge from theupper electrode plate 38, and hence the upper electrode plate 38 ischarged up, whereby the potential difference between the lower surfaceof the upper electrode plate 38 and the plasma in the processing space Sis reduced. As a result, the energy of positive ions colliding with thelower surface of the upper electrode plate 38 is reduced, and hence thelower surface of the upper electrode plate 38 is not sputtered.Silicon-based material thus does not fly off from the upper electrodeplate 38, and hence the silicon-based material does not accumulate onthe wafer W. Residue can thus be prevented from being produced on thewafer W.

Upon the RIE processing on the wafer W being completed, the supply ofthe radio frequency electrical power to the susceptor 12 by the radiofrequency power source 20 is stopped, so that the application of theradio frequency electrical power into the processing space S is stopped(step S85). At this time, the plasma in the processing space Sdisappears, whereupon the present process comes to an end.

According to the organic film processing process of FIG. 8, the upperelectrode plate 38 is put into a floating state. As a result, thepotential difference between the plasma in the processing space S andthe lower surface of the upper electrode plate 38 is reduced, and hencethe energy of positive ions colliding with the lower surface of theupper electrode plate 38 is reduced. The lower surface of the upperelectrode plate 38 is thus not sputtered, and hence the silicon-basedmaterial of the upper electrode plate 38 can be prevented fromaccumulating on the wafer.

In the present embodiment, an arrangement in which the upper electrodeplate 38 is put into a floating state is adopted. However, anarrangement in which the potential on the upper electrode plate 38 ismade to be not more than 50 eV, i.e. not more than a threshold value atwhich the sputtering yield of the silicon-based material of the upperelectrode plate 38 rises, may be adopted.

According to the plasma processing of FIG. 6, a high selectivityrelative to the resist film 65 can be secured in the etching of the SOGfilm 64, and a high selectivity relative to the amorphous carbon film 63can be secured in the etching of the SiO₂ film 62, and moreover residuecan be prevented from being produced on the wafer W in the etching ofthe amorphous carbon film 63. The inorganic film processing process andthe organic film processing process can thus be carried out on the waferW as a continuous process in the same plasma processing apparatus.

In the present embodiment described above, the plasma processingapparatus 55 has the controller 52 and the database 53. However, anexternal server and database connected to the plasma processingapparatus 55 may alternatively serve these functions.

The substrates subjected to the RIE processing or the like in the plasmaprocessing apparatus 10 or 55 described above are not limited to beingsemiconductor wafers for semiconductor devices, but rather may also beany of various substrates used in LCDs (liquid crystal displays), FPDs(flat panel displays) or the like, photomasks, CD substrates, printedsubstrates, or the like.

Moreover, it is to be understood that the present invention may also beaccomplished by supplying to a system or apparatus a storage medium inwhich is stored a program code of software that realizes the functionsof an embodiment as above, and then causing a computer (or CPU, MPU,etc.) of the system or apparatus to read out and execute the programcode stored in the storage medium.

In this case, the program code itself read out from the storage mediumrealizes the functions of the embodiments, and hence the program codeand the storage medium in which the program code is stored constitutethe present invention.

The storage medium used for supplying the program code may be, forexample, a floppy (registered trademark) disk, a hard disk, amagnetic-optical disk, an optical disk such as a CD-ROM, a CD-R, aCD-RW, a DVD-ROM, a DVD-RAM, a DVD-RW or a DVD+RW, a magnetic tape, anonvolatile memory card, or a ROM. Alternatively, the program code maybe downloaded via a network.

Moreover, it is to be understood that the functions of the embodimentscan be accomplished not only by executing a program code read out by thecomputer, but also by causing an OS (operating system) or the like whichoperates on the computer to perform a part or all of the actualoperations based on instructions of the program code.

Furthermore, it is to be understood that the functions of theembodiments can also be accomplished by writing a program code read outfrom a storage medium into a memory provided on an expansion boardinserted into the computer or in an expansion unit connected to thecomputer and then causing a CPU or the like provided on the expansionboard or in the expansion unit to perform a part or all of the actualoperations based on instructions of the program code.

1. A plasma processing method for a plasma processing apparatus having asubstrate processing chamber that has therein a processing space intowhich a substrate is transferred and is configured to carry out plasmaprocessing on the substrate in the processing space, a first electrodethat is disposed in the substrate processing chamber and is connected toa radio frequency power source, and a second electrode that has anexposed portion exposed to the processing space and is electricallyinsulated from the substrate processing chamber and the first electrode,the method comprising: a relation obtaining step of obtaining in advancea relationship between a thickness of a deposit film to be removed and arequired value of the DC voltage to be applied to the second electrodeby determining a value of the DC voltage at which the deposit film canbe removed but the second electrode itself is not sputtered for each ofa plurality of deposit film thicknesses; and a voltage value determiningstep of determining a value of the DC voltage applied to the secondelectrode from processing conditions for a plasma processing to becarried out, based on the obtained relationship; and a DC voltageapplication step of applying the DC voltage to the second electrodewithout supplying a radio frequency power to the second electrode.
 2. Aplasma processing method as claimed in claim 1, further comprising: avoltage value determining step of determining a value of the DC voltageapplied to the second electrode in accordance with an amount of depositattached to the exposed portion.
 3. A plasma processing method asclaimed in claim 1, further comprising: a voltage value determining stepof determining a value of the DC voltage applied to the second electrodein accordance with at least one of a type of a gas introduced into theprocessing space, a magnitude of radio frequency electrical powersupplied to the first electrode, and a pressure in the processing space.4. A plasma processing method as claimed in claim 1, wherein in said DCvoltage application step, the DC voltage is applied to the secondelectrode at least while the radio frequency power source is supplyingradio frequency electrical power to the first electrode.
 5. A plasmaprocessing method as claimed in claim 1, wherein in said DC voltageapplication step, the DC voltage is applied to the second electrode atleast while plasma is being produced in the processing space.
 6. Aplasma processing method as claimed in claim 1 wherein the applied DCvoltage is in a range of 50 V to 200 V.
 7. A plasma processing method asclaimed in claim 1, further comprising: a voltage value determining stepof determining a value of the DC voltage applied to the second electrodein accordance with the luminescence of the plasma in the processingspace.